Mica insulation.



J. L. COOPER & A. J. SWEET. MIGA INSULATION.

APPLIOATION FILED 0OT.18, 1905.

985,399, I Patented Feb. 28, 1911.

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WILKINSBURG, AND ARTHUR J". SWEET, 0F PITTEBURG, PENN- SYLVANIA, ASSIGNORS TO WESTINGH ELECTRIC & MANUFACTURING COM- PANY, A CORPORATION OF PENNSYLVANIA.

MICA INSULATION.

Application filed October [0 all "a bor/1. it may concern:

Be it known that we, JOHN L. Coornn and lnrm n J. Swnnr, citizens of the United States, and residents, respectively, of \Villi'insburg and of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Mica Insulation, of which the following is a specification.

Qur invention relates to sheet insulating material. for electrical conductors, and it has for its object to provide a thin. tough and flexible insulating body that shall retain its insulating properties when subjected to relatively high temperatures.

In dynamo-electric machines, and par ticularly machines which are subjected to frequent overload conditions, such as railway motors, it is desirable to provide a coilinsulation that is both flexible and tough, so that it may be easily applied to the coils and may retain its insulating pro )erties when subjected to high temperatures.

According to our invention. we provide. an insulating sheet which is built up of two strips of thin paper between which sheet nnca is assembled, the two substances adhering to each other by reason of a special insulating compound.

. Our invention is illustrated in the accompanying drawings, in which- Figure 1 is a view of an armature coil insulated in accordance therewith and Fig. 2 is a cross-section, on an enlarged scale, of the insulation of Fig. 1.

Referring to the drawings. the insulating tape which is wrapped around a coil 1 of Fig. l and is shown in cross-section in Fig. 2, comprises two outer retaining strips 2 and 3 of very thin insulating material. such as Japanese paper, between which sheets of mica 4 are assembled. The mica 4. is made to adhere to the outer retaining strips bv means of a special insulating binder. which also serves to toughen the assei'nhled insulation and to add materially to its flexibility. This compound or hinder comprises a mixture of mica-sticking varnish. wood alcohol from which the acetone has been removed and castor oil, which are preferably mixed in approximately the following proportions: four parts, wood alcohol, three parts, castor oil, one part.

Specification of Letters Patent.

18, 1905. Serial No.

I l I l l l l Patented Feb. 28, 1911. 283,342.

The material is constructed by distributing mica sheets over a sheet of thin paper to which a coating of the compound has been applied, a corresponding sheet of thin paper being placed on top ofthe mica when the desired thickness has been obtained and .sheets being finally cut into strips of desired width.

In the prior art. insulation of this character which contained sheet mica has been applied for the insulation of coils, but it was necessary to subject such coils to a. relatively expensive molding process before they could be wound in the armature slots. by reason of the nature of insulation, which was stiff and brittle and separated itself from the conductors around which it was wrapped.

The special compound of my invention makes the assembled insulation so tough and flexible that the strips may be closely wound about. the coils without interfering with their admittance into the armature slots. molding the position.

lV e claim as our invention:

1. A flexible insulation comprising sheets of. thin fabric, interposed sheet mica and abinder therefor that contains varnish, wood alcohol and castor oil.

2. A flexible insulation comprising two sheets of thin "fabric. interposed sheet mica and a binder therefor that contains approximately four parts varnish. three parts wood alcohol and one part castor oil.

3. A flexible insulating tape comprising two strips of thin paper. interposed sheet mica and a binder therefor mixture of varnish, wood alcohol and castor oil.

4. A flexible mica tape which maintains its insulating properties under high temperature. that comprises outer strips of thin paper. mica sheets assembled between said strips. and a binder that consists of a mixture of approximately four parts varnish. three. parts wood alcohol from which the acetone has been removed and one part castor oil.

5. Sheet insulating material comprising two sheets.ofthinfjfabric, interposed sheet mica and a binding material between the that comprises a not open and the mica consisting of varnish, subsc rioed our'nemes this 10th day-0i Oc wood, alcohol and castor oil. A tober, 1905.

' n comprising sheets JNO. L. COUPE ARTHUR J. SWEET.

6. A flexible insulat-io of thin fabric, interpose 5 binder therefor that con Castor oil.

ave hereunto In tes imony whereof, We h BIRNEY H1NES.

Commissioner of Patents,

five cents each, by adqlressing the Washington, D. 0.

Copies of this patent maj be obtained for 

